Table 1. Summary of Molecular Genetic Testing Used in X-linked SEDT

Gene 1Test MethodMutations Detected 2Mutation Detection Frequency by Test Method 3
MalesHeterozygous Females
TRAPPC2Sequence analysisSequence variants 4100% 580% 6
Deletion/ duplication analysis 7(Multi)exonic or whole-gene deletion/duplication20% 820%

1. See Table A. Genes and Databases for chromosome locus and protein name.

2. See Molecular Genetics for information on allelic variants.

3. The ability of the test method used to detect a mutation that is present in the indicated gene

4. Examples of mutations detected by sequence analysis may include small intragenic deletions/insertions and missense, nonsense, and splice site mutations; typically, exonic or whole-gene deletions/duplications are not detected. For issues to consider in interpretation of sequence analysis results, click here.

5. Lack of amplification by PCRs prior to sequence analysis can suggest a putative deletion of one or more exons or the entire X-linked gene in a male; confirmation may require additional testing by deletion/duplication analysis. See footnote 6.

6. Sequence analysis of genomic DNA cannot detect deletion of one or more exons or the entire X-linked gene in a heterozygous female.

7. Testing that identifies deletions/duplications not readily detectable by sequence analysis of the coding and flanking intronic regions of genomic DNA; included in the variety of methods that may be used are: quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and chromosomal microarray (CMA) that includes this gene/chromosome segment.

8. Males initially suspected on sequence analysis of having a deletion in whom the deletion is subsequently confirmed by deletion/duplication analysis

From: X-Linked Spondyloepiphyseal Dysplasia Tarda

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